In internal combustion engines such as automobiles, high-pressure fuel supply pumps for increasing the pressure of fuel are widely used in a direct injection type of fuel into a combustion chamber.
JP 5178676 A of PTL 1 discloses a high-pressure fuel supply pump having a fixing structure in which an outer periphery of a cylinder is held by a cylindrical fitting portion of a cylinder holder and a screw threaded on the outer periphery of the cylinder holder is screwed into a screw threaded on a pump body such that one cylinder end surface is brought into close contact with the pump body and the other cylinder end surface is brought into close contact with the cylinder holder.
PTL 2 discloses a hydraulic pump of a hydraulic unit for a brake device, in which a liner is fitted into a cylinder hole formed in a housing, a liner is brought into metallic contact with the housing by a caulking load at the time of caulking a periphery of a plug closing an opening of the cylinder hole, and an internal seal is formed between the housing and the liner to seal a suction side and a discharge side of the pump.